Microwave Controller using ATmega8 – AVR Project

Microwave Controller’s User Interface

Fig. Microwave Timer using AVR ATmega8

The user interface has the following parts.

Output Device: A 16×2 alphanumeric LCD Module is used as the main output device. It can display numbers, alphabets and few symbols. It can show two line and each line can have 16 characters. The backlight enables the text to be visible even in dark.

A buzzer beeps when the system receive input from the user and the input is successfully processed. For example if the user presses 10 MIN button to increment timer by 10 min and this is successfully carried out the buzzer beeps. But if the timer is already at the maximum setting (90 minutes) the operation could be carried out, so the buzzer does not beeps.

This buzzer also beeps a few time when the food is ready (countdown is finished)

Input Device: Input from user is received by a keypad which has seven push buttons. The details of button is given below.

Button

Function

Microwave

Selects Microwave mode.

Grill

Selects Grill mode.

10 MIN

Increment timer by 10 minutes.

MIN

Increment timer by 1 minute.

10 SEC

Increment timer by 1 sec.

STOP/Clear

If the microwave is in on condition, this button turns it off and pauses the timer count down.

If you are setting the timer, this button clears the time to 00:00. Useful if you have made some mistake during setting.

START

If you have paused the timer to open the oven and check the status of food, this button will resume the timer.

After time is setup you need to press this to turn the microwave (or grill).

Fig. Keypad

Controlling Relays

Their are two controlling relay

The microwave relay: this controls power to the microwave function.

The grill relay: this controls the power to the grill function.

Using the Microwave Timer

The first screen of timer asks you to choose one of the operating modes. You can choose from Microwave or Grill functions. Press the respective button on the keypad to choose the mode.

Fig. Home Screen

Then you are presented with the following screen.

Fig. "On" time input.

At the top left it shows the mode i.e. Micro for Microwave mode and Grill for Grill mode. You can press the mode keys to change the mode in this stage too.

Fig. Switching between modes.

In the center it shows the timer. Here you can set an "on" time for up to 90 minutes.

To set the time you can use the following buttons

10 MIN

To increment the timer by 10 minutes

MIN

To increment the timer by 1 minute

10 SEC

To increment the timer by 10 seconds

three buttons are provided to quickly set up desired time.

Once you are satisfied with your set time, press the START button. This will switch on the selected function (microwave or grill) and start the countdown. You can see the time decrementing on the LCD screen.

When the countdown reaches 00:00 the relay associated with the selected function (microwave or grill) will be switched off. And the screen will show Ready ! Message. When the food is ready buzzer will give long beeps few times. So that the person cooking is alerted.

At this stage (Ready) press any key to go to home screen.

Fig. Ready

Clear Function

You can press STOP/Clear button to reset the time to 00:00 during time entry.

Change Mode Function

You can press Microwave or Grill buttons (function select buttons) to change the function anytime during time entry.

Fig. Switching between modes.

Pause Function

You can press STOP/Clear button during countdown phase to pause the timer and to switch of the associated relay of selected function (microwave or grill). This will enable you to open the door of oven and have a look at the food being cooked. During this, a PAUSED! message will be displayed on the LCD. Once you are done with your inspections you can close the door and press the START button. This will resume the cooking process.

Fig. Switching between modes.

Quick Start Function

Quick start function does the following tasks at the single press of button.

Select mode Microwave.

Set on time to 30 sec.

Turn on the microwave.

Start the countdown.

You can press START button at the home screen to achieve quick start.

Once the count down has started you can press START to increase on time by 30 seconds.

Hardware for Microwave Timer

The timer is built around ATmega8 AVR microcontroller. This is a very small single chip computer which runs a small program stored in its flash memory. This program provides all the functionalities of the timer.

Our microcontroller controls the LCD Module, the relays and the buzzer. It receives user input from the keypad.

MCU Core

Microcontroller chip requires a basic circuitry for functioning. This consists of the following parts.

Power supply: This provides 5v regulated DC power to the microcontroller. It receives input 12V DC from a 12V adapter.

ISP Header: In circuit programming header. Used to easily connect an ISP Programmer to upload programs to the Microcontroller.

Reset Circuit: A pull up resistor holds the RESET pin of MCU to high state. This is required for normal operation.

Sir,
I use AVR Studio 4 & ‘eXtreeme burner” software, (with USB AVR Programer, obtained from ‘eXtreeme electronics’) to burn the chip, so can I use the same set-up for this project? Are the libraries used in this project, present in AVR Studio 4 ? Pl. give a hint…
Thanx & Regards….

I have read this project. I will certainly build one. My microwave keys are now not working. will replace the controller. My micro/and Grill has exactly the same functionality described in the post. I will begin the build in December as presently I am travelling. As per loyalty I am associated with your store since around 2007. I find your posts very informative and useful